Prostaglandin E 2 regulates the expression of connective tissue growth factor (CTGF/CCN2) in human osteoarthritic chondrocytes via the EP4 receptor

Background The regulatory mechanisms of the expression of connective tissue growth factor/CCN family member 2 (CTGF/CCN2) in human articular chondrocytes have not been clarified. We investigated the effect of prostaglandin E 2 (PGE 2 ) on CTGF/CCN2 expression in chondrocytes. Findings Articular cartilage samples were obtained from patients with osteoarthritis (OA) and chondrocytes were isolated and cultured in vitro. Chondrocytes were stimulated with PGE 2 , PGE receptor (EP)-specific agonists, or interleukin (IL)-1. CTGF expression was analyzed using quantitative polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay. The inhibitory effects of EP receptor antagonists (for EP2 and EP4) against PGE 2 stimulation were also investigated. Stimulation of chondrocytes with PGE 2 or IL-1 significantly suppressed CTGF expression. The suppressive effect of PGE 2 was reproduced by EP2/EP4 receptor agonists but not by EP1/EP3 receptor agonists, and was partially blocked by an EP4 receptor antagonist, suggesting that the EP4 receptor has a dominant role. Conclusions PGE 2 may be involved in the regulation of CTGF/CCN2 expression in human articular chondrocytes via the EP4 receptor. Elucidation of EP4-mediated signaling in chondrocytes may contribute to a better understanding of the effects of PGE 2 in arthritis.